A track roller assembly and a reduction gear apparatus of a construction machine are equipped with a ferrous floating seal for the purpose of preventing leakage of lubrication oil from inside thereof as well as entering of earth and sand therein. Accordingly, such a floating seal is widely produced by applying an adequate treatment in which a seal sliding surface thereof is quenched to have a hard martensite structure, or a large amount of hard cementite and Cr7C3 carbide are crystallized in 30% by volume while causing a parent phase to a martensite by quenching, in order to improve seizing resistance and abrasion resistance. Such an exemplary floating seal is made by using a low-alloy steel containing carbon of 0.8 wt %, a Ni-Hard cast iron or a high-carbon and high-Cr cast iron (for example, as shown in Japanese Patent Publication (KOKAI) No. S51-59007).
In addition, a ferrous floating seal member in which abrasion-resistant material is splayed to a seal sliding surface thereof is sometime used for some purposes.
In the ferrous floating seal used for sealing a lubricating oil in the reduction gears and the rollers, a seal sliding surface thereof is abraded as fine particles of earth and sand are entered on the seal sliding surface by hulling motion in the earth and sand, and is lubed with the sealed lubrication oil therein. Accordingly, a ferrous floating seal capable of withstanding a very severe lubrication condition is required. Even in a case of a most conventionally used hard ferrous floating seal made of a high-carbon and high-Cr cast iron, when setting pressure (press force) at assembling is high, considerable quenching crack (heat crack), seizing and abnormal abrasion occur on the seal sliding surface, resulting in leakage of oil.
And, even if various tool steels such as a cold work tool steel and a high speed steel (SKH material) excellent in seizing resistance are used for a floating seal, seizing caused by defect of seizing resistance and heat crack resistance easily occurs and abrasion resistance is insufficient. In addition, such steels are expensive, resulting in problem that a material cost increases in view of material yields before a product is finished.
Furthermore, in resent years, a construction machine such as a bulldozer is required to be driven at a high speed for improvement in working efficiency, and therefore, the ferrous floating seal necessarily rotates at a high speed. This also causes quenching crack, seizing and abnormal abrasion, resulting in leakage of oil.
And, a thrust bearing and a radial bearing which slides at a low speed under a high surface pressure with a severe lubricating condition of such as a bearing of a construction machine has problems in seizing, abnormal abrasion and abnormal noise. Accordingly, a ferrous abrasion resistant sliding material suitable for use in a reduction gear, a track roller and a bearing of the construction machine is required for the purpose of improving seizing resistance and preventing abnormal abrasion at sliding, and extending the abrasion resistant life.
In order to solve the above-mentioned problems, an object of the present invention is to provide a ferrous abrasion resistant sliding material capable of improving seizing resistance, abrasion resistance and heat track resistance.